Click in the empty field under the Location field to enter the URL
The url to be added is the dns domain (whatever.yourhda.com)
=== Another RDP Extension (Cross-Platform) ===
Here is another collection of RDP extensions that may fit your preferences better. Once can upload and configure these extensions almost exactly like the above.
http://waldemar.schlackow.de/node/10
== Troubleshooting: ==